December 20 - Philotrypesis caricae

In the "We Wish You a Merry Christmas" carol, there's a line in there demanding that the host bring out some figgy pudding. But there won't be much of that going around if a wasp like Philotrypesis caricae gets involved. Figs rely upon fig wasps for pollination and the close coevolutionary relationship between figs and fig wasps is one of the best examples of an animal-plant mutualism. The wasps pollinate the fig and in return, the fig wasp is provided with a secure location and an ample supply of food to raise its larvae. However, not all fig wasps are so charitable. The "grinches" in this system are parasitic, non-pollinating fig wasps that try to receive the benefits of a fig to raise their young, without paying the "admission fee" of pollinating the fig in the first place. Philotrypesis caricae is one of many hundreds of species of non-pollinator wasps which take advantage of the fig and fig wasp mutualism. The female P. carciae has a long ovipositor that allows her to penetrate through the wall of the fig to deposit her eggs directly into its interior. Furthermore the larvae of P. caricae actually outcompete the larvae of the "honest" pollinator, in this case, Blastophaga psenes. This "grinch" might not have stolen Christmas, but it sure ruined Christmas (or every other day) for many fig wasp larvae!

Contributed by Tommy Leung, with image from this site.

December 19 - Sparassis crispa

Are the lights on your Christmas tree twinkling? Beautiful ornaments hung in just the perfect spots? Tinsel icicles hanging temptingly to felines (which, should Kitty eat them, will soon result in you harkening back to some worm posts of the past year!) Well, if it's a real tree, be glad that your coniferous companion escaped parasitism by Sparassis crispa. This parasitic fungus, known as the cauliflower mushroom because of its appearance, parasitizes the roots of popular species of evergreens that are used as Christmas trees - pines, firs, and spruces. This parasite may not be so great for the tree, but they're quite nice for humans - they are edible and tasty and even now cultivated and some studies suggest that they might even be capable of stimulating the immune system.

December 18 - Haemoproteus turtur

On the second day of Christmas, my true love gave to me, two turtledoves (Streptopelia turtur)...and their blood parasite, Haemoproteus turtur? These parasites have a life cycle similar to the malaria parasites in the genus Plasmodium, but do not asexually divide in the host's blood cells, and only invade the erythrocytes as the transmission stages, the gametocytes (shown in photo). H. turtur has been shown to be vectored by the hippoboscid fly, Pseudolynchia canariensis. So, enjoy those turtledoves, true love - you're going to have 22 of them by the time the song is over - but if they get a little lethargic and don't want to "turrrr" (which is how they got their name - it doesn't have anything to do with turtles), it just might be a blood parasite to blame!

Photo by Vaidas Palinauskas.

December 17 - Viscum album

A cozy fire burning in the hearth, carols tinkling in the background, a glass of spiked eggnog in your bellies...what could be more romantic than finding yourself underneath a sprig of mistletoe hung in the archway with a sweetie, right? That is, if you don't mind kissing under a parasite. Viscum album, the European mistletoe is a parasite of more than 200 different trees and shrubs. It is hemiparasitic in that it still possesses chlorophyll but relies on its host plant for both water and other nutrients. Birds eat the juicy berries and then the seeds pass out in their feces and stick to the branch that they happen to land on, where they will germinate and set up a new parasitic plant. Mistletoe can severely damage or even kill their hosts if the infection is intense enough. The connection to Christmas is fairly recent, thought to have begun in the 18th century, and has evolved from a symbol that protected the home from fire to the more amorous excuse to kiss a pretty girl who happens to walk under it. This species, with its white berries, is more popular in Europe (and in plastic varieties everywhere); other mistletoe species (all also parasites) are used in other parts of the world.

December 16 - Desmozoon lepeophtherii

Back in July, you met Lepeophtheirus salmonis, now meet Desmozoon lepeophtherii the hyperparasite that makes a living by infecting that particular parasitic copepod. Desmozoon lepeophtherii is a microsporidian, a diverse group of unicellular parasites that are the sister group to the fungi. Microsporidians infect a wide range of animal hosts, thus it is not surprising that even a parasitic copepod is not off-limits. Interestingly, genetic analyses indicate that the closest relatives of D. lepeophtherii are microsporidian in the genus Nucleospora, which are mostly parasites of salmonids. It is possible that for some reasons, the ancestor of D. lepeophtherii opportunistically made the jump from infecting its original fish host to infecting the ectoparasites which infects the said fish.

Reference:
Freeman, M. A. and Sommerville, C. 2009. Desmozoon lepeophtherii n. gen., n. sp., (Microsporidia: Enterocytozoonidae) infecting the salmon louse Lepeophtheirus salmonis (Copepoda: Caligidae). Parasite and Vector 2:58.

Contributed by Tommy Leung.

December 15 - "Blastocystis hominis"

Single-celled organisms are difficult to classify. They don't have very much when it comes to morphology and so for a long time were just put into the large, amorphous group called "Protozoa" and treated as descending from a common ancestor. We now know that they are very divergent groups and today's parasite is a perfect example of the challenges of taxonomy. Blastocystis was originally thought to be closely related to yeasts, but then was moved to a large group called Sporozoa, which includes many well known parasites. DNA sequence data have shown, though that these parasites are part of another group known as the stramenopiles, which includes the diatoms, brown algae and Phytophthora infestans, the cause of Irish potato blight. Species of Blastocystis were classified based on the host that they had been found in, hence Blastocystis hominis. However, genetic studies showed that there is not a single species that infects humans, but rather nine or ten different subtypes, which have not yet been formally described (thus the quotation marks on the name.) Even more confusing than the taxonomy is the pathology. The protists live in the GI tract and are thought to produce typical types of GI-tract symptoms (do I have to list them?), but the symptoms reported are extremely varied and not everyone that tests positive for it shows symptoms.

December 14 - Fasciola hepatica

This parasite can be baaaaad, to sheep - and to humans. Fasciola hepatica, or the common liver fluke, is a trematode parasite with a typical complex life cycle like so many that we have seen here before, involving snails that are common around pastures. Metacercariae are ingested by grazing animals and then they seek out liver tissue and feed for a month or two, causing anemia and other symptoms in the animal. Eventually, they mature into adults and settle down in the bile ducts and just churn out eggs - about half a million a day! Humans can become infected with this parasite through accidental ingestion of the metacercariae in water, on water plants, through contact with livestock and perhaps from ingesting raw liver from infected animals.

December 13 - Eudynamys scolopaceus

This beautiful bird, commonly known as the Asian Koel, is a brood parasite in the cuckoo family. Eudynamys scolopaceus is found in southern Asia and primarily uses crows as hosts for its young. Although the female will sometimes remove one of the host's eggs when she lays hers, unlike many other brood parasites, the Asian Koel young usually do not kill or evict their nest mates, but rather beg their host parents in calls resembling those of baby crows. Their common name comes from the calls that the adults make, though their Sanskrit name, seen in literature that is more than 4000 years old, is Anya-Vapa which translates to "that was raised by others". Thus, the Asian Koel may be the first documented brood parasite known.

December 12 - Balamuthia mandrillaris

Normally, Balamuthia mandrillaris is a free-living amoeba, but on rare occasions, it has opportunistically become a parasite, with almost always fatal results. These single-celled organisms are thought to enter the body through either open wounds or perhaps inhalation and then they make their way to the brain, where they cause a disease condition called granulomatous amoebic encephalitis. Luckily cases of B. mandrillaris are extremely rare, but on the other hand, because they are rare, not much is known about their biology.

Image is from the CDC image library.

December 11 - Pelecitus fulicaeatrae

Filarial worms are nematodes that typically inhabit the body cavities and subcutaneous spaces of vertebrates. Most are viviparous (live-bearing) and their larvae, called microfilariae are found in the blood stream or subcutaneous space, where they are drawn up by biting insects when they feed. When the insects feed on a second host, the microfilariae are transferred and the life cycle starts again. Pelecitus fulicaeatrae is found in the leg joints of waster birds (coots and grebes) and its intermediate host is a louse, one more case of a parasite being the intermediate host of another parasite.

Contributed by Mike Kinsella and photo by Julia Diaz.